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Rocketsonde buoy system : observing system simulation experiments

University of British Columbia

The research presented here provides measurements of the negative impact of the Pacific and Arctic data voids on numerical weather predictability downstream over North America, and the extent to which the detrimental effects can be mitigated with rocket soundings from anchored buoys within the Rocketsonde Buoy System (RBS). The goals include the optimum deployment locations in the Pacific data void, rocketsonde sensor requirements, optimum height of the sounding profiles, number and configuration of the RBS array, real-time management requirements, daily launch times, launch periods during the year, number of rockets per buoy, and resulting buoy size. Observing System Simulation Experiments (OSSEs) are performed that assimilate virtual rocket soundings into an initial weather analysis and then measure the resulting change in forecast skill relative to reference forecasts. OSSEs are performed for 1 day in 2001, 21 days in 2002, 19 days in 2003 and 6 days in 2004. Reference forecast results are studied for 382 days. It is found that the optimum profile height is 6 km. Wintertime-storm forecast-error over western North America averages 18-25% more than summertime, rising to double for high-impact events. The forecasts from 00Z analyses score 6-12% better than the forecasts from 12Z analyses. The RBS engineering constraint is currently 200 of the 6 km altitude rocketsondes allowing a seven-month RBS operational period centered on the winter months delivering a daily 12Z profile. RBS mass and wind observations contribute fairly equally, sometimes cumulatively, to the forecast. A 5% launch tilt is acceptable. Compared to eastern North America, western North America has an averaged penalty of 20%, increasing to 35% during storms, caused by the Pacific data void. A 20% averaged improvement from better Pacific initialization is realistic. During high-impact situations, a three to six RBS strategic deployment can achieve 0.70 or more of this goal. On average, a six-RBS deployment delivers a 0.30 improvement; a 12-15 RBS deployment provides a 0.60 improvement. Real-time management and targeted-RBS operations enhance the results. In summary, deployment of an RBS is recommended because it would likely improve forecast skill over much of North America.

Text

2009-12-23

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http://hdl.handle.net/2429/17204

Atmospheric Science

University of British Columbia

UBCV

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